STRUCTURE OF THE WHITE COLUMNS OF THE SPINAL CORD. 335 



believe otherwise than that the tissue immediately surrounding 

 the nerve fibres, the neuroglia, which presents the same cha- 

 racters also in the grey substance of the spinal cord, is a 

 peculiarly modified form of connective tissue, the semi-solid 

 matrix of which is finely granular instead of being fibrillated, 

 or is even structureless, as the observations of Walther,* which 

 were made on the frozen brains of living animals, appear to 

 establish. If the latter be true, the finely granular character 

 of the neuroglia must be regarded as the result of coagulation 

 occasioned by the treatment the tissue has previously under- 

 gone with hardening agents. This finely granular or perhaps 

 primarily structureless matrix, as is not very uncommonly the 

 case with the ordinary fibrillated connective tissue (of serous 

 membranes) is traversed in all directions by plexuses of fine 

 elastic fibres, and contains cellular elements consisting of con- 

 nective-tissue corpuscles in various stages of development. In 

 regard to the occurrence of the latter, Henle and Merkel,f 

 proceeding from the well-known observations of Cohnheim on 

 the formation of pus, have advanced a very interesting hypo- 

 thesis to the effect that they are to be regarded as escaped 

 white corpuscles of the blood. 



The nerve fibres of the white substance have as their es- 

 sential constituent an axial fibre, or axis-cylinder, the diameter 

 of which stands in tolerably constant relation to the size of the 

 nerve fibre, amounting to about one-third or one-fourth of its 

 breadth. In preparations that have been slightly hardened 

 with salts of chromic acid, and subsequently treated with 

 alkalies, the finely striated aspect of the axis-cylinder, when 

 examined with high powers, cannot escape observation, and I 

 entirely concur with the excellent description of the axis-fibre 

 already given in this work (p. 154, vol. i.) by Max Schultze. 

 A second constituent that scarcely ever fails in fully developed 

 nerve fibres of the white substance is the nerve medulla, or 

 medullary sheath, for the histological and micro-chemical rela- 

 tions of which I must likewise refer to the essay of M. Schultze. 

 In fine sections of the spinal cord, especially after treatment with 



* Medicmische Centralblatt. Jahrg., 1868, p. 450. 

 t Loc. cit., p. 79. 



